All laboratory compaction and design tests for use in flexible pavement design must duplicate the unit weight (density) of the ultimate in-place pavement materials. Some paving materials compaction and design tests employ a tamping foot (impact or kneading) as the compaction method where the number of tamps of a given magnitude are empirically correlated with the unit weight (density) developed under traffic. These procedures become obsolete when the traffic load changes. Some later developments in paving materials compaction and design tests employ a gyratory kneading action at a given magnitude of vertical stress and angle of kneading in which the number of cycles of kneading are empirically correlated with the unit weight (density) developed under traffic. These test methods also become obsolete when the traffic loads increase above that for the empirically correlated condition.
Other machines used previously for measuring the shear strength and dynamic moduli (compression and rebound) under cyclic loading have simply employed cyclic loading on a confined or unconfined cylinder of the paving material the cylinder receiving no added distortional stress in conjunction with the cyclic vertical stress. This is not analogous to the action occurring in a flexible pavement layer beneath a moving wheel as the pavement layer actually deflects under the load thus introducing a combined action of internal particle movement or so-called kneading action in conjunction with the vertical compression and rebound with the passage of the wheel load.
Examples of conventional arrangements and/or methods are disclosed in the following patents, the teachings of which are hereby incorporated in their entirety by reference:
______________________________________ PAT. NO. PATENTEE ______________________________________ 2,972,249 McRae et al. 3,127,765 O'Neil 3,397,572 Stolz et al. 3,478,572 McRae et al. 3,618,369 Hamilton et al. 4,502,338 Smith et al. 4,569,222 Arnold et al. 4,942,768 McRae 5,036,709 McRae 5,275,056 Hamilton 5,323,655 Eagan 5,456,118 Hines ______________________________________